Crystal structure, magnetic, and dielectric properties of Aurivillius-type Bi3Fe0.5Nb1.5O9

摘要

Bi3Fe0.5Nb1.5O9 was synthesized using conventional solid state techniques and its crystal structure was refined by the Rietveld method using neutron powder diffraction data. The oxide adopts an Aurivillius-type structure with non-centrosymmetric space group symmetry A2(1)am (a = 5.47016(9) angstrom, b = 5.43492(9) angstrom, c = 25.4232(4) angstrom), analogous to other Aurivillius compounds that exhibit ferroelectricity. The Fe and Nb cations are disordered on the same crystallographic site. The [(Fe,Nb)O-6] octahedra exhibit tilting and distortion to accommodate the bonding requirements of the Bi cations located in the perovskite double layers. Magnetic measurements indicate non-Curie-Weiss-type paramagnetic behavior from 300 to 6 K. Measurements of dielectric properties and electrical resistivity exhibited changes near 250-260 degrees C and are suggestive of a ferroelectric transition. (C) 2007 Elsevier Inc. All rights reserved.